According to a new Buzzfeed report, the top stories from fake news sources attracted more engagement on Facebook than the top stories from legitimate news organisations in the weeks leading up to the election, generating more shares, comments and reactions on the social network.

On the websites they tracked, Buzzfeed found four of the five top performing stories came from fake news sites, with a single article from The Washington Post reaching the level of engagement achieved by stories like “WikiLeaks CONFIRMS Hillary Sold Weapons to ISIS” and “FBI Agent Suspected in Hillary Email Leaks Found Dead in Apparent Murder-Suicide” between August and election day.

That analysis appears to contradict comments Facebook CEO Mark Zuckerberg made in the days after the election. Speaking at the Techonomy business conference on Thursday, Zuckerberg said he doubted fake news stories on Facebook affected the results of the election, as they represent “a very small amount of the content” on the site, a thought he later expanded upon on his own Facebook page.

“Of all the content on Facebook, more than 99% of what people see is authentic,” wrote Zuckerberg. “Only a very small amount is fake news and hoaxes. The hoaxes that do exist are not limited to one partisan view, or even to politics. Overall, this makes it extremely unlikely hoaxes changed the outcome of this election in one direction or the other.”

Zuckerberg’s claim that hoaxes are not partisan seems equally suspect. According to Buzzfeed’s analysis, 17 of the 20 top-performing fake election stories were “overtly pro-Donald Trump or anti-Hillary Clinton.” And on Monday, Gizmodo reported that Facebook developed a tool to fight fake news stories that ended up disproportionately affecting right-wing news sites (the tool was never deployed).

Gizmodo has reached out to Facebook for comment. This post will be updated if and when they respond. [Buzzfeed]